Let the number of stamps of 20p and 25p be x and y respectively.
Then as per the question
x + y = 47 …….(i)
0.20x + 0.25y = 10
4x + 5y = 200 …….(ii)
From (i), we get
y = 47 – x
Now, substituting y = 47 – x in (ii), we have
4x + 5(47 – x) = 200
⇒ 4x – 5x + 235 = 200
⇒ x = 235 – 200 = 35
Putting x = 35 in (i), we get
35 + y = 47
⇒ y = 47 – 35 = 12
Hence, the number of 20p stamps and 25p stamps are 35 and 12 respectively.
